Electronic circuits having a power field effect transistor (FET) with a field plate provide advantages over conventional power field effect transistors. Power FETs include a semiconductor body having a drain zone, a drift zone, a source zone and a body zone. Field plates are introduced to reduce the on-resistor Ron and to reduce switching losses in the Miller phase. The field plate shields the electric field in the drift region from the gate. This structure also increases the breakdown voltage by reducing the carrier concentration in the drift zone. The field plate may also be called shield electrode.
In many applications, a high output capacitance Coss limits the performance of the power field effect transistor. The output capacitance Coss includes the drain-to-source capacitance CDS and the gate-to-drain capacitance CGD. Typically, the drain-to-source capacitance is the dominating part of the output capacitance Coss. The drain-to-source capacitance includes typically the capacitance of the isolating layer between body zone and drift zone and the capacitance of the dielectric between the field plate and the drift zone in series with the capacitance of the depleted